Problem: If $x \bigtriangledown y = xy+2x-y$ and $x \triangleleft y = 3x-5$, find $5 \bigtriangledown (4 \triangleleft 1)$.
Explanation: First, find $4 \triangleleft 1$ $ 4 \triangleleft 1 = (3)(4)-5$ $ \hphantom{4 \triangleleft 1} = 7$ Now, find $5 \bigtriangledown 7$ $ 5 \bigtriangledown 7 = (5)(7)+(2)(5)-7$ $ \hphantom{5 \bigtriangledown 7} = 38$.